UCLA

HYPOTHESIS: Endolymphatic hydrops (EH) associated with cochlear implantation are associated with vestibular dysfunction. BACKGROUND: Vestibular dysfunction is a known risk after cochlear implantation (CI). CI has been shown to cause cochlear hydrops due to fibrosis surrounding the ductus reuniens. However, the association of cochlear hydrops with vestibular hydrops and the relationship to vestibular symptoms remain unknown. METHODS: Histopathological analysis and clinical evaluation of the vestibular end organs of 17 human temporal bones (HTB)s exhibiting cochlear hydrops from 15 CI recipients. RESULTS: Eight of 15 patients with cochlear hydrops due to CI had complaints of dizziness, vertigo, or imbalance following CI. In all 17 HTBs with cochlear hydrops, there was fibrosis, atrophy, or obstruction of the ductus reuniens, and all had straight electrode CI via cochleostomy. In one of the eight reporting postoperative dizziness, labyrinthitis ossificans was deemed causative. Six of the seven remaining patients had EH of both the saccule and utricle. Fifteen of 17 HTBs (88.2%) had saccular EH. In contrast, 8 of 17 HTBs (47.0%) in 7 patients had utricular EH, of which 6 patients had postoperative vertigo spells. It seems that hydrops of the utricle closely corresponds to postoperative vertigo spells and vestibular complaints. CONCLUSION: Implantation of the CI, when complicated by ductus reuniens fibrosis, may cause both cochlear hydrops and vestibular endolymphatic hydrops. Hydrops of the vestibular periphery when involving the utricle seems to be more likely associated with disabling vertigo symptoms. This study supports the round window technique of insertion rather than cochleostomy.